The invention relates to a fluid vectoring nozzle.
In particular it relates to a fluid vectoring nozzle in which, in operation, vectoring of fluid flow in the nozzle is achieved by selectively producing a fluid dynamic throat in the nozzle.
Control of the flow direction of fluid exiting a pipe, duct or nozzle is known as a means of controlling the direction of travel of air, land and water based vehicles. For example by vectoring thrust from the exhaust nozzle of an aircraft the direction of the aircraft can be affected, thereby making the aircraft more maneuverable. In a land based vehicle (for example, in a hovercraft) vectored thrust can be used to the same effect to replace rudders or where the vehicle is slow moving and hence a conventional rudder is of limited use. Water based vehicles may also control their direction by controlling the direction of fluid exiting a water propulsion device, thereby steering the craft.
Such devices work by controlling a portion of the nozzle at nozzle exit. Hence whatever direction the nozzle exit points in is the direction the fluid will travel in, thereby causing a reaction force that steers the vehicle.
Alternatively a moveable grille, vent or vane assembly arrangement may be provided at nozzle exit, which, by setting the vanes at an angle to the axis of the nozzle, alters the direction of fluid flow exiting the nozzle.
Such devices require the use of moveable mechanical parts to be placed in the nozzle fluid flow. The reliability of the moveable parts is clearly critical since directional control of the associated vehicle depends on their operation. Any device in the fluid flow path of an exhaust nozzle of a gas turbine or water propulsion device will have to cope with foreign object damage, dirt and debris affecting pivotable bearing joints, as well as withstanding the physical force induced by the thrust of the fluid. Hence such devices must either be made robust enough to last long hours or be capable of being easily maintained or replaced. In both cases the maintenance cost of such a device will be high, and the design and construction will be complex in order to deliver a reliable product. Additionally, the provision of a moveable grille, vent or vane assembly will also introduce turbulence into the exhausted fluid, thereby contributing the amount of noise produced by the exhausted fluid.
Flow vectoring devices employing fluid injection are also known. These operate by injecting fluid at an angle to the direction of the bulk fluid flow through a nozzle. The injected fluid creates a fluidic obstruction or ramp which deflects the bulk fluid flow towards the opposing duct wall thereby altering its direction of travel. Such devices are disadvantaged in high aspect ratio nozzles (i.e. a wide but shallow duct) where it is required to vector the fluid flow from left to right. In such an embodiment the fluid injection would need to be through the side of the duct, and the obstruction/ramp effect is diminished by the width of the nozzle, requiring a large mass flow of fluid to be injected to obtain a minor vectoring effect.
Hence a device which can control the directional flow of fluid at exit from a nozzle and yet not require moveable parts to be placed in the fluid flow passing through the nozzle, which can reduce operational noise levels of the engine, and which enables effective flow vectoring in nozzles in which other flow vectoring devices have reduced effectiveness, is highly desirable.